What to read after Morality from Compassion?

According to Arthur Schopenhauer, compassion is the basis of morality. He sees concern for justice as a negative form of compassion, directed at not harming anyone, as opposed to the more far-reaching, positive form of benefiting. He thinks a higher degree of compassion involves realizing that the spatio-temporal separation of individuals is illusory and that in reality they are all identical. Such compassion is impartial and all-encompassing. Compassion is suited to be the centre of morality because its object are negative feelings, and only these are real. Contrary to these Schopenhauerian claims, it is here argued that compassion must be supplemented with attitudes like sympathy and benevolence because positive feelings exist alongside negative feelings; that a concern for justice, though morally essential, is independent of these attitudes which are based on empathy; that these attitudes involve not identifying oneself with others, but taking personal identity as
insignificant in empathically imagining how others feel. Schopenhauer is however right that, though these attitudes are spontaneously partial, this can be corrected. His morality is also interesting in raising the question rarely discussed in philosophical ethics of how moral virtue relates to ascetic self-renunciation. Both of these ideals are highly demanding, but the book ends by arguing that this is no objection to their validity.